From EP 1 963 625 B1 a generic camshaft is known, with an outer shaft and with an inner shaft, arranged coaxially thereto, rotatable with respect to the outer shaft at least in a limited manner.
Owing to the necessary freedom of movement between the inner shaft and the outer shaft in an adjustable camshaft or respectively also owing to a necessary conveying of oil for a phase adjuster or respectively a bearing lubrication, usually an annular gap with a radial height of 0.2 mm to 2 mm is provided between the inner shaft and the outer shaft. A seal at the end of the two shafts is necessary here, in order to be able to build up and hold the oil pressure, necessary for the phase adjuster, between the inner shaft and the outer shaft. In inner shafts known from the prior art, these are, for example, thickened in the region of a sealing ring, which can be achieved for example by a material removal on almost the complete length of the inner shaft adjacent to the sealing ring. However, this is comparatively expensive.